Anti-glare film and process for producing same thereof

ABSTRACT

Disclosed are an antiglare film having a high level of anti-scintillation properties, high sharpness of transmitted images, high light transmittance (total light transmittance), and a high level of external light reflection preventive properties, and a process for producing the antiglare film. A resin and non-agglomerative particles having a specific particle diameter are selected so that the difference in refractive index between the resin and the particles is 0.05 to 0.15. The resin and the non-agglomerative particles are brought to a coating composition using, as a solvent, a good solvent for the resin and a poor solvent for the resin. The coating composition is coated onto a substrate film to form a coating which is then dried. In the course of the drying, as the amount of the good solvent in the coating decreases, the poor solvent acts to cause the gelation of the particles and the resin. Thus, good concaves and convexes can be advantageously formed on the surface of the coating. The layer thus formed can meet various property requirements for antiglare films.

TECHNICAL FIELD

[0001] This invention relates to an antiglare film which, when disposedon the front of CRTs (cathode ray tubes) displays or liquid crystaldisplays, serves to diffuse light externally incident on these displays,thereby reducing glare.

BACKGROUND ART

[0002] In CRT displays, accelerated electrons collide with phosphorslocated on the inner side of the front glass to impart energy to thephosphors. This permits the phosphors to emit light, and, in general,red, green, and blue lights outgo on the front side. In liquid crystaldisplays, the liquid crystal per se does not emit light. Since, however,light is applied from the backside to enhance the visibility of liquidcrystal images, on the whole of the display, light is emitted toward thefront.

[0003] When the display is used in a room, light from lightingequipment, such as a fluorescent lamp, enters the surface of the displayand is reflected from the display surface. This causes glaring of thedisplay screen or reflection of a fluorescent lamp on the displayscreen, making it difficult to perceive letters and the like displayedon the screen.

[0004] The disposition of an antiglare film, having a light diffusinglayer formed by coating a silica-containing resin coating compositiononto a transparent substrate film, on the front of the display todiffuse external light causative of glare, and consequently to alleviatethe glare of the display screen, has been already carried out in theart.

[0005] Conventional antiglare films include one wherein concaves andconvexes have been formed on the surface of a light diffusing layerthrough the agglomeration of particles of agglomerative silica or thelike, one wherein resin beads having a larger particle diameter than thethickness of the coating have been added to impart concaves and convexeson the surface of the coating, and one wherein an embossing film havingconcaves and convexes on its surface had been laminated onto the surfaceof an unsolidified coating to transfer the shape of concaves andconvexes onto the surface of the coating followed by the separation ofthe embossing film.

[0006] All the above conventional antiglare films have light diffusingproperties, a certain level of antiglare effect, and, in addition, byvirtue of the thin film form, can be easily applied to displays.

[0007] However, when light emitted from the display toward the front ispassed, through the antiglare film, shining called “scintillation”occurs on the film surface, disadvantageously posing a problem ofdeteriorated visibility of displayed images.

[0008] The following properties are important for an antiglare filmwhich, in use, is disposed on the front of a display: (1) high level ofanti-scintillation properties; (2) high image sharpness; (3) high lighttransmittance (=total light transmittance); and (4) high antiglareproperties derived from light diffusing properties (=high level ofcapability of preventing the reflection of external light from afluorescent lamp or the like external light reflection preventiveproperties)). None of the conventional antiglare films simultaneouslysatisfy all the above property requirements.

DISCLOSURE OF THE INVENTION

[0009] Accordingly, it is an object of the present invention to providean antiglare film simultaneously satisfy all of the propertyrequirements, that is, (1) high anti-scintillation properties, (2) highsharpness of transmitted images, (3) high total light transmittance, and(4) high external light reflection preventive properties withoutsignificantly altering the form of the conventional antiglare film, thatis, the thin film form, and a process for producing the same.

[0010] The present inventors have found that, in the formation of anantiglare film by coating of a resin coating composition with particlesdispersed therein, the formation of good concaves and convexes and theprovision of an antiglare film satisfying various properties required oflight diffusing films can be realized by a method which comprises thesteps of: selecting a resin and non-agglomerative particles having aspecific article diameter so that the difference in refractive indexbetween the resin and the particles is 0.05 to 0.15; bringing the resinand the non-agglomerative particles to a coating composition using, as asolvent, a good solvent for the resin and a poor solvent for the resin;coating the coating composition onto a substrate film to form a coating;and drying the coating, whereby, in the course of the drying, as theamount of the good solvent contained in the coating decreases, the poorsolvent acts to cause the gelation of the particles and the resin.

[0011] According to one aspect of the present invention, there isprovided an antiglare film comprising at least a light diffusing resinlayer formed of non-agglomerative light-transparent fine particlesdispersed in a light-transparent resin, the light-transparent fineparticles having a particle diameter of 1.0 to 5.0 μm, the difference inoptical refractive index between the light-transparent fine particlesand the light-transparent resin being 0.05 to 0.15, the content of thelight-transparent fine particles being 5 to 30 parts by weight based on100 parts by weight of the light-transparent resin, the surfaceroughness of the light diffusing resin layer being 0.12 to 0.30 in termsof center line average roughness (Ra) and 1.0 to 2.9 in terms often-point average roughness (Rz).

[0012] In another embodiment of the antiglare film according to thepresent invention, the light diffusing resin layer is stacked on atransparent substrate.

[0013] According to the present invention, the thickness of the lightdiffusing resin layer is preferably 1 to 3 times the diameter of thelight-transparent fine particles.

[0014] According to the present invention, the antiglare film preferablyhas an image sharpness of 80 to 300 and a level of external lightreflection preventive properties of 5 to 70.

[0015] According to another preferred embodiment of the presentinvention, the light-transparent resin is a cured product of an ionizingradiation-curable resin.

[0016] According to another aspect of the present invention, there isprovided a process for producing an antiglare film, comprising the stepsof:

[0017] providing a coating composition comprising non-agglomerativelight-transparent fine particles, a light-transparent resin, a goodsolvent for the light-transparent resin, and a poor solvent for thelight-transparent resin, the light-transparent fine particles having aparticle diameter of 1.0 to 5.0 μm, the difference in optical refractiveindex between the light-transparent fine particles and thelight-transparent resin being 0.05 to 0.15, said ingredients beingcontained in the coating composition in an amount of 5 to 30 parts byweight for the light-transparent fine particles based on 100 parts byweight of the light-transparent resin and in an amount of 20 to 1,000parts by weight for the solvent in terms of the total amount of the goodsolvent and the poor solvent, the parts by weight ratio of the goodsolvent to the poor solvent being 100:20 to 100:70;

[0018] coating the coating composition onto a substrate; and

[0019] then drying the coating to reduce the weight ratio of the goodsolvent to the light-transparent resin, whereby, while allowing thelight-transparent fine particles and the light-transparent resin to gel,the coating is solidified to create concaves and convexes on the surfaceof the coating.

[0020] According to a preferred embodiment of the present invention, thelight-transparent resin and the good and poor solvents are selected fromthe following combinations:

[0021] (a) a combination of an acrylate resin, a good solvent for theacrylate resin selected from the group consisting of toluene, methylethyl ketone, ethyl acetate, n-butyl acetate, and cyclohexanone, and apoor solvent for the acrylate resin selected from the group consistingof methanol, ethanol, n-butanol, and isopropanol;

[0022] a combination of a cellulosic resin, a good solvent for thecellulosic resin selected from the group consisting of ethyl acetate,n-butyl acetate, acetone, and cyclohexanone, and a poor solvent for thecellulosic resin selected from the group consisting of methanol,ethanol, n-butanol, and isopropanol;

[0023] (c) a combination of an epoxy resin, a good solvent for the epoxyresin selected from the group consisting of methanol/toluene (“/”referring to mixing), ethanol/xylene, methyl ethyl ketone, ethylacetate, n-butyl acetate, and methyl isobutyl ketone, and a poor solventfor the epoxy resin selected from the group consisting of toluene,xylene, cyclohexanone, and cyclopentane;

[0024] (d) a combination of a urea melamine resin, a good solvent forthe urea melamine resin selected from the group consisting of ethylacetate, n-butyl acetate, n-butanol, and n-hexyl alcohol, and a poorsolvent for the urea melamine resin selected from the group consistingof toluene and xylene; and

[0025] (e) a combination of a urethane resin, a good solvent for theurethane resin selected from the group consisting of ethyl acetate,n-butyl acetate, and methyl ethyl ketone, and a poor solvent for theurethane resin selected from the group consisting of methanol andethanol.

[0026] In the above process, the drying is preferably carried out at atemperature of 20 to 100° C.

[0027] According to another embodiment of the process, thelight-transparent resin is an ionizing radiation-curable resin and,after the formation of concaves and convexes on the surface of thecoating, an ionizing radiation is applied to the coating to cure thecoating through crosslinking.

BRIEF DESCRIPTION OF THE DRAWING

[0028]FIG. 1 is a cross-sectional view of the antiglare film accordingto the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0029] The embodiments of the present invention will be described withreference to FIG. 1. An antiglare film 1 according to the presentinvention basically has a laminate structure comprising a transparentsubstrate 2 and a light diffusing resin layer 3 stacked on thetransparent substrate 2. The light diffusing resin layer 3 internallycontains light-transparent fine particles 4 and has fine concaves andconvexes 5 on its surface.

[0030] In the formation of the light diffusing resin layer to bycoating, the transparent substrate 2 is an object to be coated with thelight diffusing resin layer 3 and thus is in most cases necessary.Alternatively, a casting method may be used which comprises providing areleasable substrate instead of the transparent substrate 2, coating alight diffusing resin layer 3 on the surface of the releasablesubstrate, and then separating the releasable substrate from the lightdiffusing resin layer 3. According to the casting method,self-supporting light diffusing resin layer 3 not provided with thetransparent substrate 2 can be obtained.

[0031] Materials for constituting the antiglare film according to thepresent invention, the mixing ratio of the materials, the surfaceroughness of the antiglare film, solvents (good solvent and poorsolvent) used in the production of the antiglare film according to thepresent invention, drying and the like will be successively described.

[0032] The non-agglomerative light-transparent fine particlesconstituting the antiglare film according to the present invention havean optical refractive index very close to the light-transparent resinwhich will be described next, and, thus, when dispersed in thelight-transparent resin, are transparent. The diameter of thelight-transparent fine particles is preferably in the range of 1.0 to5.0 μm. When the particle diameter is less than 1.0, the addition of thelight-transparent fine particles to the light-transparent resin does notprovide satisfactory light diffusing properties. On the other hand, whenthe particle diameter exceeds 5.0 μm, the image sharpness and the lighttransmittance are unsatisfactory.

[0033] Specific examples of non-agglomerative light-transparent fineparticles usable herein include organic non-agglomerativelight-transparent fine particles, such as styrene beads (refractiveindex 1.60), melamine beads (refractive index 1.57), acryl beads(refractive index 1.49), acryl-styrene beads (refractive index 1.54),polycarbonate beads, polyethylene beads, and polyvinyl chloride beads.Among them, styrene beads and acryl-styrene beads are preferred.

[0034] Among the non-agglomerative light-transparent fine particles,inorganic non-agglomerative light-transparent fine particles usableherein include fine particle of SiO₂ (refractive index 1.5 to 2.0),Al—SiO₂ (refractive index 1.65), and GeO (refractive index 1.65). Amongthem, fine particles of SiO₂ are preferred.

[0035] Since all the above light-transparent fine particles arenon-agglomerative, the difference in refractive index between thelight-transparent fine particles and the light-transparent resin caneffectively offer internal scattering properties, and thus can preventscintillation.

[0036] Light-transparent resins include a crosslinking-cured product ofan ionizing radiation-curable resin, a cured product prepared bycrosslinking of an ionizing radiation-curable resin together with asolvent evaporation type resin, particularly thermoplastic resin, and acured product of a thermosetting resin.

[0037] Among them, resins belonging to the category of ionizingradiation-curable resins are mainly acrylate oligomers or prepolymers,or monofunctional or polyfunctional monomers. Oligomers or prepolymersinclude relatively low-molecular weight polyester resin, polyetherresin, acrylic resin, epoxy resin, urethane resin alkyd resin,spiroacetal resin, polybutadiene resin and polythiol-polyene resin andacrylate or methacrylate (acrylate and methacrylate being hereinaftercollectively referred to as “(meth)acrylate”) of polyhydric alcohols orthe like.

[0038] These ionizing radiation-curable resins may contain the followingmonofunctional monomers or polyfunctional monomers as a reactivediluent. Monofunctional monomers include ethyl (meth)acrylate,ethylhexyl (meth)acrylate, styrene, methylstyrene, and N-pyrrolidone,and polyfunctional monomers include trimethylolpropanetri(meth)acrylate, hexanediol (meth)acrylate, tripropylene glycoldi(meth)acrylate, diethylene glycol di(meth)acrylate, pentaerythritoltri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, and neopentyl glycol di(meth)acrylate. Thesemonofunctional monomers or polyfunctional monomers may be cured as suchby crosslinking without the oligomer or the prepolymer, or alternativelymay be used as a mixture thereof with a thermoplastic resin or athermosetting resin.

[0039] Preferred solvent evaporation type resins, which may be added tothe ionizing radiation-curable resin, are mainly cellulosic resinsbecause of high transparency, and examples thereof includenitrocellulose resin, acetylcellulose resin, cellulose acetatepropionate resin, and ethylhydroxyethylcellulose resin

[0040] Thermosetting resins usable as the light-transparent resininclude phenolic resins, urea resins, diallyl phthalate resins, melamineresins, guanamine resins, unsaturated polyester resins, polyurethaneresins, epoxy resins, aminoalkyd resins, urea-melamine resins, andsilicone resins.

[0041] When the thermosetting resin is used, if necessary, for example,a crosslinking agent or a polymerization initiator may be added.

[0042] In the antiglare film according to the present invention, thedifference in optical refractive index between the light-transparentfine particles and the light transparent resin should be 0.05 to 0.15.Regarding the refractive index of the light-transparent resin, theionizing radiation-curable resin has a refractive index of about 1.5. Inthe case of other resins, when the optical refractive index is low, therefractive index difference is sometimes larger than the acceptablerefractive index difference. This sometimes results in loweredtransparency of the light-transparent fine particles. In this case, fineparticles having high optical refractive index, for example, fineparticles of TiO₂ (refractive index 2.3 to 2.7), Y₂O₃ (refractive index1.87) La₂O (refractive index 1.95), ZrO₂ (refractive index 2.05), orAl₂O₃ (refractive index 1.63) may be added to the light-transparentresin to enhance the refractive index of the light-transparent resin,thereby regulating the difference in refractive index between thelight-transparent resin and the light-transparent fine particles.

[0043] The non-agglomerative light-transparent fine particles are addedin an amount of 5 to 30 parts by weight based on 100 parts by weight ofthe light-transparent resin. When the amount of the non-agglomerativelight-transparent fine particles added is less than 5 parts by weight,satisfactory light diffusing properties cannot be provided. Therefore,the anti-scintillation properties and the external light reflectionpreventive properties of the antiglare film are unsatisfactory. When theamount of the non-agglomerative light-transparent fine particles addedexceeds 30 parts by weight, the light-diffusing properties can beimproved. In this case, however, the haze is increased resulting inlowered sharpness of transmitted images, and, in addition, the lighttransmittance (=total light transmittance) is unfavorably lowered.

[0044] The antiglare film according to the present invention preferablyhas the following specified surface roughness. Specifically, the centerline average roughness (Ra) is 0.12 to 0.30, and the ten-point averageroughness (Rz) is 1.0 to 2.9. The center line average roughness (Ra) andthe ten-point average roughness (Rz) may be determined according to themethods specified in JIS B 0601.

[0045] Here the center line average roughness (Ra) is 0.12 to 0.30, andthe ten-point average roughness (Rz) is 1.0 to 2.9.

[0046] In the antiglare film according to the present invention, thethickness of the light diffusing resin layer is preferably 1 to 3 timesthe diameter of the light-transparent fine particles internallydispersed in the light diffusing resin layer. The antiglare filmaccording to the present invention is produced by the process of thepresent invention, described below, using a good solvent and a poorsolvent, and concaves and convexes are formed on the surface of thecoating through a mechanism of drying in the course of the productionprocess. Therefore, even though the layer thickness clearly exceeds thediameter of the fine particles to such an extent that the fine particlesare internally embedded in the light diffusing resin layer, theantiglare film can have the surface roughness specified above.

[0047] When the thickness of the light diffusing resin layer is smallerthan the diameter of the light-transparent fine particles internallydispersed in the light diffusing resin layer, the concaves and convexesformed on the layer surface are large, leading to deterioratedanti-scintillation properties. On the other hand, when the thickness ofthe light diffusing resin layer is more than 3 times the diameter of thelight-transparent fine particles, increasing the amount of the fineparticles added is necessary for forming concaves and convexes havinggood shape on the surface of the layer. This increases the haze andconsequently lowers the sharpness of transmitted images and the totallight transmittance.

[0048] According to the antiglare film of the present invention,specifying the particle diameter of the light-transparent fineparticles, the difference in refractive index between thelight-transparent fine particles and the light-transparent resin, themixing ratio between the light-transparent fine particles and thelight-transparent resin, and the surface roughness can provide excellentproperties of the antiglare film, that is, a level of sharpness oftransmitted images of 80 to 300 and a level of external light reflectionpreventive properties of 5 to 70.

[0049] The sharpness (distinctness) of a transmitted image is determinedaccording to JIS K 7105. Specifically, light transmitted through orreflected by a sample is measured through a moving optical comb by usinga measuring apparatus for the sharpness of an image, and the sharpnessof the transmitted image is calculated from the results by the followingequation:

C=(M−m)/(M+m)×100

[0050] wherein

[0051] C represents sharpness of transmitted image, %;

[0052] M represents maximum wave height; and

[0053] m represents minimum wave height.

[0054] The larger the value of the sharpness C (%) of the transmittedimage, the higher the sharpness of the image and the better the qualityof the image. The apparatus used is an image clarity measuring apparatus(ICM-1DP) manufactured by Suga Test Instruments Co., Ltd. In the opticalcomb, four slit widths are used. Therefore, the maximum value is100%×4=400%.

[0055] The level of the external light reflection preventive propertiesmay be measured as follows. A black pressure-sensitive adhesive tape isapplied to a light diffusing resin layer on its side not having concavesand convexes as a sample to prevent the reflection of light from thebackside. While this sample is kept horizontal, a parallel light fluxhaving a size of 5 mm square is applied to the sample at an angle of 10degrees to the normal thereof. The light flux reflected on the lightdiffusing resin layer in its side having concaves and convexes isobserved from the regular reflection direction by means of a CCD camera.The aperture of the CCD camera is regulated to bring the luminance ofthe peak to a given value, and the inclination angle of the luminance atthe inflection point of the luminance in the edge portion of thereflected light flux. This inclination angle is regarded as the level ofexternal light reflection preventive properties. When a light flux isreflected on a specular surface, the inclination of the luminance issubstantially equal to 90 degrees. In the case of a matte surface havinglarge concaves and convexes, the inclination of the luminance issmaller.

[0056] The “external light reflection” in the item of evaluation ofantiglare films prepared in examples and comparative examples describedbelow refers to the level of external light reflection preventiveproperties determined in this way.

[0057] In the production of the antiglare film according to the presentinvention, non-agglomerative light-transparent fine particles are mixedwith a light-transparent resin, the mixture is dispersed or dissolved ina solvent composed of a good solvent for the light-transparent resin anda poor solvent for the light-transparent resin to prepare a coatingcomposition, and the coating composition is coated onto a substrate toform a coating which is then dried to cure the coating.

[0058] In the coating composition, the solvent (the good solvent and thepoor solvent being collectively referred to as “solvent”) is used in anamount of 20 to 1,000 parts by weight based on 100 parts by weight ofthe light-transparent resin. In this case, the parts by weight ratio ofthe good solvent to the poor solvent in the solvent is 100:20 to 100:70.

[0059] The term “good solvent” refers to a solvent having an excellentcapability of dissolving or swelling the resin, and the term “poorsolvent” refers to a solvent which has a poor capability of dissolvingthe resin and is likely to, cause the gelation of the resin. In thisconnection, the following matter should be noted. Both a suitable goodsolvent and a suitable poor solvent vary depending upon each resin asthe solute. Further, probably, whether the solubility is excellent orpoor is relatively determined. Examples of combinations of typicallight-transparent resins with good and poor solvents for thelight-transparent resins include:

[0060] a) a combination of an acrylate resin, a good solvent for theacrylate resin selected from the group consisting of toluene, methylethyl ketone, ethyl acetate, n-butyl acetate, and cyclohexanone, and apoor solvent for the acrylate resin selected from the group consistingof methanol, ethanol, n-butanol, and isopropanol;

[0061] b) a combination of a cellulosic resin, a good solvent for thecellulosic resin selected from the group consisting of ethyl acetate,n-butyl acetate, acetone, and cyclohexanone, and a poor solvent for thecellulosic resin selected from the group consisting of methanol,ethanol, n-butanol, and isopropanol;

[0062] c) a Combination of an epoxy resin, a good solvent for the epoxyresin selected from the group consisting of methanol/toluene (“/”referring to mixing), ethanol/xylene, methyl ethyl ketone, ethylacetate, n-butyl acetate, and methyl isobutyl ketone, and a poor solventfor the epoxy resin selected from the group consisting of toluene,xylene, cyclohexanone, and cyclopentane;

[0063] d) a combination of a urea melamine resin, a good solvent for theurea melamine resin selected from the group consisting of ethyl acetate,n-butyl acetate, n-butanol, and n-hexyl alcohol, and a poor solvent forthe urea melamine resin selected from the group consisting of tolueneand xylene; and

[0064] e) a combination of a urethane resin, a good solvent for theurethane resin selected from the group consisting of ethyl acetate,n-butyl acetate, and methyl ethyl ketone, and a poor solvent for theurethane resin selected from the group consisting of methanol andethanol.

[0065] In the above combinations, two or more good solvents and/or twoor more poor solvents may be used for the light-transparent resin.

[0066] In the coating composition, the amount of the solvent is 20 to1,000 parts by weight based on 100 parts by weight of thelight-transparent resin. When the resin or monomer used has highsolubility, the amount of the solvent may be small. On the other hand,when the resin or monomer used has relatively low solubility or, upondissolution in the solvent, forms a highly viscous solution, the amountof the solvent used is increased.

[0067] When the amount of the solvent used is below the lower limit ofthe specified amount range, upon the evaporation of only a small amountof the solvent, the viscosity is increased or otherwise gelation occurs.This is a source of trouble in the production of the antiglare film. Onthe other hand, when the amount of the solvent used is above the upperlimit of the specified amount range, much energy is required for theevaporation of the solvent to dry the coating.

[0068] The parts by weight ratio of the good solvent to the poor solventin the solvent is 100:20 to 100:70.

[0069] A coating composition, wherein the amount of the poor solventused is below the lower limit of the specified amount range, isdisadvantageous in that, since the major proportion of the solvent isaccounted for by the good solvent, upon coating of the coatingcomposition, the whole solvent rapidly disappears making is difficultfor concaves and convexes to be formed on the surface of the coating bymere drying. On the other hand, when the poor solvent is contained in anamount larger than the upper limit of the specified amount range,gelation proceeds in an early stage. This is likely to result in theformation of large concaves and convexes. Further, in this case, thereis a fear of the coating composition causing gelation during storage,and, in addition, when the evaporation rate of the poor solvent is slow,there is a possibility that the coating is less likely to be dried.

[0070] The relative evaporation rate R of the solvent may be used as ameasure of evaporation rate of the solvent. The relative evaporationrate R of the solvent A is determined using, as a standard, the timerequired for n-butyl acetate to be evaporated at room temperature, andcalculated by the equation R=[time required for n-butyl acetate to beevaporated]/[time required for solvent A to be evaporated]. The largerthe value of R, the higher the evaporation rate, and the smaller thevalue of R, the lower the evaporation rate.

[0071] Preferably, the relative evaporation rate R is not more than 3.7for the good solvent, and not more than 1.9 for the poor solvent. Thegood solvent and the poor solvent arch preferably selected so that therelative evaporation rate R of the good solvent is higher than that ofthe poor solvent. Since, however, the good solvent and the poor solventshould also be selected by taking into consideration the parts by weightratio of the good solvent to the poor solvent and the capacity of adryer for drying after coating of the coating composition, the relativeevaporation rate R of the good solvent selected is in some cases lowerthan that of the poor solvent.

[0072] When the coating composition satisfies a requirement such thatthe amount of the solvent (the good solvent and the poor solvent beingcollectively referred to as “solvent”) is 20 to 1,000 parts by weightbased on 100 parts by weight of the light-transparent resin and theparts by weight ratio of the good solvent to the poor solvent in thesolvent is 100:20 to 100:70, this coating composition is free fromgelation during storage and other problems, and can maintain a viscositysuitable for coating.

[0073] Materials for the substrate to be coated with the coatingcomposition in the formation of the light diffusing resin layer includetransparent glass and transparent resins. The transparent resin may bein the form of a film, a sheet, or a plate.

[0074] An example of transparent resin is a resin wherein hydroxylgroups of cellulose have been partially or entirely esterified mainlywith a lower fatty acid. Specific examples of such resins includeacetylcellulose and cellulose acetate butyrate, typically cellulosetriacetate. Further, various polyesters (typically polyethyleneterephthalate=PET), acryl (typically polymethyl methacrylate),polyurethane, polycarbonate, polymehtylpentene, (meth)acrylonitrile,polyethersulfone, polysulfone, polyetherketone and the like may also beused.

[0075] Among them, a film of the transparent resin is more preferredbecause the film of the transparent resin can permit continuous coating,can provide a flexible antiglare film which is highly compatible withvarious applications. The film thickness of the transparent resin isgenerally 25 to 100 μm.

[0076] As described above, when the substrate to be coated with thecoating composition has a releasable surface, upon the formation of thelight diffusing resin layer, the substrate may be separated from thelight diffusing resin layer to provide a self-supporting light diffusingresin layer not having any substrate. In some cases, the substrateinherently has poor adhesion to the light diffusing resin layer due tothe relationship between the material for the substrate and the materialfor the light diffusing resin layer. In this case, there is no need tointentionally render the surface of the substrate releasable.Alternatively, when the formation of the self-supporting light diffusingresin layer is contemplated, a method may also be used wherein thecoating composition is coated onto a specular surface of a metal or thelike to form a layer followed by the separation of the layer from thespecular surface or the like.

[0077] The coating composition may be coated onto the substrate by aconventional coating or printing method. Examples of coating andprinting methods include: coating methods, such as roll coating, gravureroll coating, spray coating, curtain flow coating, flow coating, kisscoating, roll coating using a spinner-whirler or the like, and brushcoating; and printing methods, such as gravure printing and silk screenprinting.

[0078] When drying is carried out after coating onto the substrate,concaves and convexes are formed on the surface of the coating as thedrying proceeds.

[0079] As soon as the coating composition is coated onto the substrateby the coating or printing method, drying is initiated. To this end, itis common practice to perform blowing of air and/or heating. Under theseconditions, the solvent is gradually evaporated.

[0080] As the amount of the solvent contained in the coating compositionconstituting the wet coating decreases, the light-transparent resin,present near the surface, which has been in the state of dissolutionowing to the action of the good solvent, begins to gel due to thepresence of the poor solvent. This leads to the formation of a solidcomprised of the light-transparent resin and the light-transparent fineparticles around the surface of the coating. In the gelation, the higherthe evaporation rate of the good solvent as compared with the poorsolvent, the higher the drying temperature, or the larger the flow ofair blown, the higher the rapidity in reduction of the solvent and thehigher the rapidity in the formation of the solid comprised of thelight-transparent resin and the light-transparent fine particles whichresult in the formation of relatively large concaves and convexes. Onthe other hand, when the evaporation rate of the good solvent is notvery higher than that of the poor solvent or when drying conditions aremilder, the speed of reduction in the solvent contained in the coatingcomposition is lower. In this case, relatively fine concaves andconvexes are formed.

[0081] Further, the smaller the amount of the good solvent contained inthe coating composition, the higher the rapicity in gelation. In thiscase, relatively large concaves and convexes are formed.

[0082] That is, according to the production process of the presentinvention, the size of concaves and convexes formed on the surface ofthe coating can be regulated by regulating the difference in evaporationrate between the good solvent and the poor solvent, drying conditions,and the proportion of the good solvent in the solvent. Since theconcaves and convexes on the surface of the coating are not governed bythe size of the light-transparent fine particles, different size levelsof concaves and convexes can be advantageously formed even whenlight-transparent fine particles having the same size are used.

[0083] While retaining the concaves and convexes formed on the surfaceof the coating, the coating can be solidified by continuing the drying,or cured by a suitable method according to the resin component in thecoating composition used. Specifically, in the case of a thermosettingresin, if necessary, heat is further applied, and, in the case of anionizing radiation-curable resin, an ionizing radiation is applied toperform curing through crosslinking.

EXAMPLES Example 1

[0084] The following materials were thoroughly mixed together accordingto the following formulation to prepare a coating composition for alight diffusing resin layer. Light-transparent resin 100 pts. wt. Pertaerythritol triacrylate (PET 30, manufactured by Nippon Kayaku Co.,Ltd.) Photoinitiator  5 pts. wt. (Irgacure 184, manufactured byCIBA-GEIGY Ltd.) Tight-transparent fine particles  8 pts. wt.Polystyrene resin filler (particle diameter 1.3 μm, refractive index1.6) Good solvent 60 pts. wt. Methyl isobutyl ketone (relativeevaporation rate R 1.6) Poor solvent 15 pts. wt. Isbutvl alcohol(relative evaporation rate R 0.64)

[0085] A cellulose triacetate film (TD-80U, thickness 80 μm,manufactured by Fuji Photo Film Co., Ltd.) was provided as a substrate.The coating composition prepared above was roll coated onto one side ofthe substrate. The coating was then dried at a temperature of 50° C. toform concaves and convexes on the surface of the coating, followed byapplication of ultraviolet light at 120 mJ to cure the coating. Thus, anantiglare film was prepared.

Examples 2 to 7 and Comparative Examples 1 to 5

[0086] For Examples 2 to 7 and Comparative Examples 1 to 4, in thecoating composition used, the light transparent resin and photoinitiatorused and amounts thereof were the same as used in Example 1, and thelight transparent fine particles and the solvent were varied. The otherconditions were the same as those used in Example 1, except that thelayer thickness and the drying temperature were varied.

[0087] For Comparative Example 5, only pentaerythritol triacrylate wascoated onto an embossing film having concaves and convexes on itssurface to a thickness of 3 μm to form a coating which was then curedand separated.

[0088] The difference between Example 1 and the other examples and thecomparative examples and the like are shown in Tables 1 and 2 below.TABLE I Light transparent fine particles: Material Good Solvent: Poorsolvent: Layer Particle diameter/refractive Name Name thickness Ex.index/amount in pts. wt. R/amount in pts. wt. R/amount in pts. wt.Drying temp. Ex. 1 Polystyrene Methyl isobutyl Isobutanol 3 μm 1.3/1.6/6pts. wt. 1.6/60 pts. wt. 0.64/15 pts. wt. 50° C. Ex. 2 Same as Ex. 1Same as Ex. 1 Same as Ex. 1 3 μm 70° C. Ex. 3 Same as Ex. 1 Same as Ex.1 except Same as Ex. 1 except same as that the amount was that theamount was Ex. 1 changed to 52.5 changed to 22.5 pts. wt. pts. wt. Ex. 4{circle over (1)} Polystyrene n-Butyl acetate Isopropanol 3 μm 1.3/1.6/4pts. wt. 1.0/60 pts. wt. 1.5/40 pts. wt. 70° C. {circle over (2)} ″1.5/1.55/4 pts. wt. Ex. 5 Polystyrene Toluene Ethanol 5 μm 3.5/1.6/12pts. wt. 2.0/40 pts. wt. 1.54/35 pts. wt. 80° C. Ex. 6 PolystyreneCyclohexanone Isopropanol 8 μm 5/1.6/8 pts. wt. 0.32/65 pts. wt. 1.5/35pts. wt. 60° C. Ex. 7 Polystyrene Xylene n-Butanol 8 μm 4/1.6/9 pts. wt.0.76/40 pts. wt. 0.47/35 pts. wt. 100° C. 

[0089] TABLE 2 Light transparent fine particles: Material Good Solvent:Poor solvent: Layer Comp. Particle diameter/refractive Name Namethickness Ex. index/amount in pts. wt. R/amount in pts. wt. R/amount inpts. wt. Drying temp. Comp. Same as Ex. 1 Methyl isobutyl 3 μm Ex. 1ketone 70° C. 1.6/75 pts. wt. Comp. Same as Ex. 1 Isobutanol 3 μm Ex. 20.64/75 pts. wt. 70° C. Comp. {circle over (1)} Agglomerative silicaToluene 3 μm Ex. 3 1/2/1.45/3 pts. wt. 2.0/75 pts. wt. 70° C. {circleover (2)} ″ 1.7/1.45/3 pts. wt. Comp. Agglomerative silica Isobutanol 3μm Ex. 4 1.7/1.45/6 pts. wt. 0.64/75 pts. wt. 70° C. Comp. 3 μm Ex. 550° C.

[0090] The antiglare films prepared in the examples and the comparativeexamples were evaluated, and the results are shown in Tables 3 and 4.

[0091] In Tables 3 and 4, the “scintillation” was determined by puttinga color filter (staggered grid arrangement or triangular arrangement,pitch 150 μm; in order to avoid the influence of color, the color filterconsists of black matrix only and the filter on each pixel is notcolored) on a backlight for a liquid crystal display (LIGHTBOX 45,manufactured by HAKUBA) and fixing the antiglare film to a positiondistant by 160 μm from the surface of the color filter in such a mannerthat the antiglare film on its side having concaves and convexes was onthe viewer side, and inspecting the surface of the film by means of aCCD camera to determine the standard deviation of a variation inluminance. TABLE 3 Ex. No. Item Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex.7 Transmittance 91.2 91 91.2 91.5 91 91.4 91 Haze 13.3 15 19.3 8.6 24.714 16 Internal haze 5 5 5 3.5 9 6 6.5 Scintillation 10 12 13 14 9 12 11Sharpness 124 100 80 139 157 95 107 External light 60 53 26 56 36 45 51reflection preventive properties Ra 0.174 0.185 0.197 0.167 0.186 0.2300.191 θa 2.33 2.15 2.68 2.04 3.45 2.24 2.09 Rz 1.19 1.67 2.21 1.76 2.192.78 1.97 Rmax 1.31 2.14 3.14 1.83 2.31 2.93 2.46 Sm 40.0 52.6 50.8 47.648.8 40 55

[0092] TABLE 4 Ex. No. Comp. Comp. Comp. Comp. Comp. Item Ex. 1 Ex. 2Ex. 3 Ex. 4 Ex. 5 Transmittance 91.7 89 91.2 90.6 92.3 Haze 17 45 11 214.5 Internal haze 15 3 0.3 0.3 0 Scintillation 9 14 19 14 41 Sharpness325 15.9 40 32 276 External light 87 3.5 45 19 80 reflection preventiveproperties Ra 0.105 1.40 0.328 0.365 0.111 θa 0.94 5.11 2.20 3.44 1.1 Rz0.38 7.72 2.93 3.01 0.64 Rmax 0.41 11.5 3.16 3.53 0.75 Sm 131 118 42.153.7 89.3

[0093] Example 1 is different from Example 2 only in drying temperature.The antiglare film of Example 1 using a lower drying temperature, ascompared with the antiglare film of Example 2, had finer concaves andconvenes and, by virtue of this, possessed better scintillation andsharpness of transmitted image (the sharpness of transmitted image beinghereinafter and in tables referred to simply as “sharpness”). Theantiglare film of Example 2 using a higher drying temperature, ascompared with the antiglare film of Example 1, had higher surfaceroughness. Due to the higher surface roughness, the level of externallight reflection preventive properties was better although the sharpnesswas lower and the haze was somewhat higher.

[0094] In Example 3, the proportion of the poor solvent was higher thanthat in Example 1. Due to the higher proportion of the poor solvent,despite the fact that the crying temperature in Example 3 was the sameas that in Example 1, the surface roughness was higher than that in thecase of Example 2 using a higher drying temperature than Example 1.Therefore, the level of external light reflection preventive propertieswas further improved, although the sharpness was lower and the haze washigher.

[0095] In Example 4, 50% of the fine particles used was accounted for byfine particles having a refractive index of 1.5 which was close to therefractive index of the resin. Due to the lower haze, the sharpness wassomewhat higher. Although the level of scintillation was inferior tothat in Example 1 due to lower internal haze, this level ofscintillation was satisfactory from the practical point of view.

[0096] In Examples 5 to 7 wherein the diameter of fine particles and thesolvent were varied, the properties of the antiglare films were as goodas those in Example 1 and other examples.

[0097] In Comparative Example 1 wherein the solvent consisted of thegood solvent alone, concaves and convexes were less likely to be formedon the surface and, consequently, the surface was substantially flat.This provided inferior external light reflection preventive properties,although the scintillation and the sharpness were good.

[0098] In Comparative Example 2 wherein the solvent consisted of thepoor solvent alone, considerably large concaves and convexes were formedto constitute a frosted glass-like surface. This results in loweredlight transmittance and very low sharpness.

[0099] In Comparative Example 3, the sharpness was poor although thescintillation and the external light reflection preventive propertieswere good.

[0100] In Comparative Example 5 wherein, unlike the examples and theother comparative examples, an embossing film was used to form concavesand convexes and the fine particles were not added, the absence of thefine particles provided good transmittance and sharpness. However, thescintillation and the level of the external light reflector preventiveproperties were not satisfactory.

[0101] According to the present invention wherein the light-transparentresin and the light-transparent fine particles in a resin layer and thesurface roughness of the resin layer were specified, an antiglare filmhaving such a resin layer possesses excellent properties, that is,possesses a high level of anti-scintillation properties, a high level ofsharpness of transmitted images, and high light transmittance (=totallight transmittance) while enjoying a high level of external lightreflection preventive properties.

[0102] According to a preferred embodiment of the present invention, theantiglare film is provided with a transparent substrate. Thisconstruction can advantageously offer good strength and goodhandleability at the time of production and fabrication.

[0103] According to the present invention, unlike the prior art, thethickness of the resin coating is larger than the diameter of the fineparticles. Therefore, the antiglare film is durable.

[0104] Further, according to the present invention, sharp images can beprovided on a display using this antiglare film, and the visibility ofimages is satisfactory even under an environment exposed to externallight or under illumination. Further, according to a preferredembodiment of the present invention, the resin layer is formed of acrosslinking-cured product of an ionizing radiation-curable resincomposition. The antiglare film having this resin layer possessesexcellent physical and chemical properties.

[0105] According to the production process of the present invention, anantiglare film having desired concaves and convexes can be produced byproperly selecting good and poor solvents, mixing ration, dryingtemperature and other conditions, without necessarily limiting thediameter of fine particles to be incorporated.

[0106] Further, according to a preferred embodiment of the presentinvention, a solvent may be selected from highly general-purposesolvents to produce the antiglare film.

[0107] According to the production process of the present invention, anantiglare film having excellent physical and chemical properties can bestably produced by forming concaves and convexes using an ionizingradiation-curable resin and applying an ionizing radiation to thecoating to cure the coating through crosslinking.

What is claimed is:
 1. An antiglare film comprising a light diffusingresin layer formed of non-agglomerative light-transparent fine particlesdispersed in a light-transparent resin, the light-transparent fineparticles having a particle diameter of 1.0 to 5.0 μm, the difference inoptical refractive index between the light-transparent fine particlesand the light-transparent resin being 0.05 to 0.15, the content of thelight-transparent fine particles being 5 to 30 parts by weight based on100 parts by weight of the light-transparent resin, the surfaceroughness of the light diffusing resin layer being 0.12 to 0.30 in termsof center line average roughness (Ra) and 1.0 to 2.9 in terms often-point average roughness (Rz).
 2. The antiglare film according toclaim 1, wherein the light diffusing resin layer is formed on atransparent substrate.
 3. The antiglare film according to claim 1,wherein the thickness of the light diffusing resin layer is 1 to 3 timesthe diameter of the light-transparent fine particles.
 4. The antiglarefilm according to claim 1, which has an image sharpness of 80 to 300 anda level of external light reflection preventive properties of 5 to 70.5. The antiglare film according to claim 1, wherein thelight-transparent resin is a cured product of an ionizingradiation-curable resin.
 6. A process for producing an antiglare film,comprising the steps of: providing a coating composition comprisingnon-agglomerative light-transparent fine particles, a light-transparentresin, a good solvent for the light-transparent resin, and a poorsolvent for the light-transparent resin, the light-transparent fineparticles having a particle diameter of 1.0 to 5.0 μm, the difference inoptical refractive index between the light-transparent fine particlesand the light-transparent resin being 0.05 to 0.15, said ingredientsbeing contained in the coating composition in an amount of 5 to 30 partsby weight for the light-transparent fine particles based on 100 parts byweight of the light-transparent resin and in an amount of 20 to 1,000parts by weight for the solvent in terms of the total amount of the goodsolvent and the poor solvent, the parts by weight ratio of the goodsolvent to the poor solvent being 100:20 to 100:70; coating a surface ofa substrate with the coating composition; and drying the coating toreduce the weight ratio of the good solvent to the light-transparentresin, whereby, while allowing the light-transparent fine particles andthe light-transparent resin to gel, the coating is solidified to createconcaves and convexes on the surface of the coating.
 7. The process forproducing an antiglare film according to claim 6, wherein thelight-transparent resin and the good and poor solvents are selected fromthe following combinations: (a) a combination of an acrylate resin, agood solvent for the acrylate resin selected from the group consistingof toluene, methyl ethyl ketone, ethyl acetate, n-butyl acetate, andcyclohexanone, and a poor solvent for the acrylate resin selected fromthe group consisting of methanol, ethanol, n-butanol, and isopropanol;(b) a combination of a cellulosic resin, a good solvent for thecellulosic resin selected from the group consisting of ethyl acetate,n-butyl acetate, acetone, and cyclohexanone, and a poor solvent for thecellulosic resin selected from the group consisting of methanol,ethanol, n-butanol, and isopropanol; (c) a combination of an epoxyresin, a good solvent for the epoxy resin selected from the groupconsisting of methanol/toluene (“/” referring to mixing),ethanol/xylene, methyl ethyl ketone, ethyl acetate, n-butyl acetates,and methyl isobutyl ketone, and a poor solvent for the epoxy resinselected from the group consisting of toluene, xylene, cyclohexanone,and cyclopentane; (d) a combination of a urea melamine resin, a goodsolvent for the urea melamine resin selected from the group consistingof ethyl acetate, n-butyl acetate, n-butanol, and n-hexyl alcohol, and apoor solvent for the urea melamine resin selected from the groupconsisting of toluene and xylene; and (e) a combination of a urethaneresin, a good solvent for the urethane resin selected from the groupconsisting of ethyl acetate, n-butyl acetate, and methyl ethyl ketone,and a poor solvent for the urethane resin selected from the groupconsisting of methanol and ethanol.
 8. The process for producing anantiglare film according to claim 6, wherein the drying is carried outat a temperature of 20 to 100° C.
 9. The process for producing anantiglare film according to claim 6, wherein the light-transparent resinis an ionizing radiation-curable resin and, after the formation ofconcaves and convexes on the surface of the coating, an ionizingradiation is applied to the coating to cure the coating throughcrosslinking.